As rage2299 stated, make sure the clip isn't deformed. I once had trouble trouble getting the drive axle back in. Making a 90 degree turn on to a street one day months after I did the job, I heard a loud bang. I stopped but failed to find anything wrong. A few days later is saw the axle seal leaking on the side I had worked on previously. I guess with the hard time I had getting the axle in I deformed the clip too much and it never expanded back fully when I hammered it in. When I was removing the axle, as soon as I took it out of the knuckle, the axle was already loose. I didn't have to use a puller, proof it was not mounted properly in the trans. I replace the seal and bought a rubber faced 3 lb dead blow hammer to replace the 12 oz. light duty one I used the time previous. The bigger hammer made a huge difference. I wasn't strong enough to push it in with my hands.
